The redundant outer tie rod assembly protects against failure of an outer tie rod connection to a steering knuckle in a rack and pinion steering system.
The tie rod of a vehicle rack and pinion steering system has an inner tie rod connector assembly that is connected to a rack of the rack and pinion steering system and an outer tie rod connector assembly that is connected to a steering knuckle. The inner and outer tie rod connector assemblies must accommodate vertical movement of the steering knuckle about a virtual or actual fore and aft extending axis formed by the suspension system. Pivotal movement about an axis of the king pin and horizontal movement of the rack toward and away from the steering knuckle must also be accommodated by the inner and outer tie rod connector assemblies. These movements all decrease when the steering system is employed to steer the rear wheels of a vehicle with four wheel steering. However the decreased movements must be accommodated. Ball and socket connections between the steering rack and the inner end of the tie rod as well as between the steering knuckle and an outer end of the tie rod are the preferred connections.
Ball and socket connections, like all mechanical connections can fail. Failures, if they do occur, are most likely due to a long period of use, inadequate lubrication or a joint overload. These failures may be in a part that breaks, a tie rod housing crimp that retains a ball in a socket, in threads that attach one of the ball joint members to the steering knuckle, in the steering rack or in a tie rod shank. Looseness in ball and socket joints connected to the front steered wheels of a vehicle can be detected as excess free travel in the steering wheel. Such looseness is an indication that there could be a tie rod connector failure. Looseness in the ball and socket joints of the rear steered wheels of a vehicle with four wheel steering is generally not detectable as free play in the steering wheel.
The front steered wheels of a vehicle have a steering geometry that includes caster, camber and toe in. This geometry tends to move the front steered wheels to positions which direct the vehicle straight forward if the operator releases the steering wheel or if a ball joint fails. Rear steered wheels generally have a different geometry. Due to the different geometry rear steered wheels may not tend to return to a straight forward position if a ball joint in the steering linkage fails. Wear or damage to the ball joints in a rear wheel steering systems is more difficult to detect and a failure of one of these ball joints may make a vehicle unstable.
The vehicle steering linkage for steering a vehicle wheel includes a first link and a second link. A primary connection between the first link and the second link includes a ball fixed to one of the links and a socket that retains the ball and is fixed to the other one of the first and second links. A redundant connection between the first link and the second link includes a slot through the first link and a retainer that is attached to the second link, passes through the slot and has a large head which prevents separation of the of second link from the first link. Steering forces pass through the primary connection prior to failure of the primary connection. Steering forces pass through the redundant connection following failure of the primary connection.